The first can I got at a body shop supply store on Broadway in Denver. Then I discovered that regular "cold galvanizing compound" from any hardware store is actually the same stuff, something like 95-97% zinc. It's half the price and saves a trip into the middle of Denver. I use it on inside surfaces which will be welded and can't be subsequently accessed.

Hey Ian, thanks so much for that square tube you gave me! It's been a long time, but I finally got around to using it.

For the skin, to replace what I cut out of the quarter panel, I cut some strips, then drilled them. The holes are to weld them to the wings in the channel. After I cut and drilled them, I sprayed what will be the inside surface with cold weld-through zinc.